For Ubuntu, where those variables are defined, the 000-init-whitelist plugin calls update-rc.d and prevents those services from starting on boot. A lot of those services are significant, for example cups (for printer sharing), ondemand (so that thin client CPUs don't overheat), sendsigs (for proper shutdown), binfmt-support (if wine or java apps are installed on the chroot), openbsd-inetd (if ident2 is installed on the chroot for squid), etc etc, see attached file.

Is there any reason for those white lists to be defined? Can we comment them out like Debian does?

I'm not too familiar with the whitelisting magic used by ltsp-build-client but my guess would be that we should instead use a blacklist.

We definitely want to prevent a lot of services from starting when they don't make sense for LTSP but not prevent fat client services.

I also think ltsp-build-client should be made upstart aware so it can also disable upstart services.

Assigning this to me for now as I'm probably going to look at upstartifying ltsp soon enough and may fix that at the same time. In the mean time, if you have changes specific to fat clients, I'd suggest you commit them upstream and make sure they only apply to fat clients.